The present invention relates, in general, to the field of fibre channel switching technology. More particularly, the present invention relates to non-disruptive, on-line testing and switchover in a high availability, fibre channel switching environment.
Fibre Channel is a high performance, serial interconnect standard designed for bi-directional, point-to-point communications between servers, storage systems, workstations, switches, and hubs. It offers a variety of benefits over other link-level protocols, including efficiency and high performance, scalability, simplicity, ease of use and installation, and support for popular high level protocols.
Fibre channel employs a topology known as a xe2x80x9cfabricxe2x80x9d to establish connections between ports. A fabric is a network of switches for interconnecting a plurality of devices without restriction as to the manner in which the switch can be arranged. A fabric can include a mixture of point-to-point and arbitrated loop topologies.
In Fibre Channel, a channel is established between two nodes where the channel""s primary task is to transport data from one point to another at high speed with low latency. The Fibre channel switch provides flexible circuit/packet switched topology by establishing multiple simultaneous point-to-point connections. Because these connections are managed by the switches or xe2x80x9cfabric elementsxe2x80x9d rather than the connected end devices or xe2x80x9cnodesxe2x80x9d, fabric traffic management is greatly simplified from the perspective of the device.
In a high availability, fibre channel switching environment, a second set of xe2x80x9credundantxe2x80x9d elements are provided in the event of a failure condition. The number and make-up of the redundant elements parallel the primary elements, and operate as back-up resources if the primary elements fail. As such, in the event of such a fail condition, a switchover to the redundant elements can greatly minimize the loss of transmitted data frames.
In prior approaches, the redundant elements in a high availability environment are passive in nature. This approach provides a second set of elements that remain inactive until the occurrence of a fail condition. In such an all-or-nothing passive environment, it becomes necessary to take a system offline to perform the necessary tests on the elements to determine if they are still in working condition. Since taking a system offline is often not a viable option, the unfortunate effect is a lack of a significant method of testing the redundant elements. As a result, switching over to the redundant elements may result in a situation where an element is either partially or completely non-functional.
Another limitation of prior systems is that during switchover to the redundant elements in a failure condition, frames were lost, since there was no implementation of a completely seamless method of transition to the redundant elements. It is well understood that for a catastrophic failure event, immediate switchover is of paramount importance. However, for a non-catastrophic failure, the significance of immediacy becomes secondary to the importance of maintaining the integrity of a frame transmission.
The on-line testing and switchover design of the present invention provides a solution to the aforementioned problems which is vastly superior to anything currently available. It not only solves the critical situation where, after switchover, an element is either partially or completely non-functional, but it does so in an extremely efficient manner without requiring any significant design changes and with only a relatively straightforward alteration to existing processes for networking in a high availability, fibre channel switching environment.
The present invention advantageously provides a proactive management approach for verifying the integrity of a redundant switching element prior to actual use. More particularly, the on-line testing and switchover design of the present invention offers independent, non-disruptive online testing via an independent request/response signaling interface on a per port basis. Since the invention operates on a per port basis, it is unnecessary to shut down the other operating ports to carry out the testing operation, and therefore the ports can continue to transmit data. In addition, the invention advantageously provides the ability to switch over to a redundant switching element on a frame boundary, thereby reducing the possibility of losing a frame during the transition from a currently functioning path to a backup path.
Particularly disclosed herein is a method of performing an online, non-disruptive health check test in a fully redundant fibre channel switching network having an active switching element and a redundant switching element. The health check test is performed on the redundant switching element without the need to take the network offline. After a first and second status condition are met prior to the expiration of a timer, a working data path from a port to the redundant switching element is verified and the condition is recorded. Then, a working control path to the redundant switching element is verified and the condition is recorded.
In another aspect, the present invention provides a method of performing automatic switchover in a fully redundant fibre channel switching network having an active switching element, a redundant switching element and a port having switching element logic embodied therein. To begin, a failure condition is detected in the active switching element. The failure condition is transmitted to the port logic. In response to a possible problem with the active switching element, software notifies the port logic to perform the switchover. Notification may originate from either the active switching element or port logic via software collection. In response, the port is queried to determine if the port is transmitting a frame. If a port is in the process of transmitting a frame, then the automatic switchover is delayed until the port is not transmitting a frame.
Still further disclosed herein is a fibre channel switching network having increased bandwidth capacity. The network comprises a first switching element, a second switching element, a first reader coupled to the first switching element and a second reader coupled to the second switching element. Continuing, the switching network also has a buffer memory for storing frames, wherein the buffer memory is coupled to the first reader and the second reader. The network also has a writer coupled to the buffer memory, wherein the writer directs a buffer control to store frames in the buffer memory. The first reader or the second reader directs the buffer control to retrieve a frame from buffer memory and pass the frame to the respective reader for transmission.